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Measuring Waveforms
3-78
CSA8000B & TDS8000B User Manual
High (mode)
Low (mode)
Low (min/max)
High (min/max)
High (mean)
Low (mean)
Mid reference
Figure 3- 20: High/Low tracking methods
H Mean (of Histogram) sets the values statistically. Using a histogram, it
selects the mean or average value derived using all values either above or
below the midpoint (depending on whether it is defining the high or low
reference level). This setting is best for examining eye patterns and optical
signals. See Figure 3--20.
H Min-max uses the highest and lowest values of the wavef orm rec or d. This
setting is best for examining wavefor ms that have no lar ge , fla t portions at a
common value, such as sine waves and triangle waves — almost any waveform
except for pulses. See Figure 3--20.
H Auto switches between methods. Auto method first attempts to calculate the
high and low values using the Mode method. Then, if the histogram does not
show obvious consistent high and low levels, Auto method automatically
switches to the Min/Max or Mean method.
For example, the Mode histogram operating on a triangle wave would not
find consistent high and low levels, so the instrument would switch to
the Min/Max mode. Consistent high and low levels would be found on a
square wave, so the Auto mode would use the Mode method.
When setting High/Low method, be aware of these operating behaviors:
H The tracking settings are not global; that is, you can independently set the
method used for each of Meas 1 -- Meas 8.
H You can turn off tracking for either or both the High and Low levels and
enter them directly.
H Not all tracking methods are appropriate for all measurements. If you cannot
set the tracking method, the controls will be disabled.